Spatial and temporal changes of benthic macroinvertebrate assemblages in acidified streams in the Bohemian Forest (Czech Republic)

Outflows from two atmospherically acidified lakes in the Bohemian Forest were studied in 2005 and 2007. While Lake ?ertovo has been strongly acidified (～pH 4.6), Lake Laka was only slightly acidified in the past and is recovering now (～pH 5.2). The water chemistry and macrozoobenthos composition were analysed along longitudinal gradients of both lake outflows to determine the present status of their streams. A certain progression in stream chemistry to more neutral conditions was observed along the longitudinal gradients of both streams. However, a possible recovery of macrozoobenthos was evident only in the Lake Laka outflow, mainly via an increasing number of Ephemeroptera and Trichoptera taxa, and an increasing number of Gammarus fossarum, both along the longitudinal gradient and during the period of study. In contrast, no considerable changes were observed in the macrozoobenthos composition of the Lake ?ertovo outflow, presumably because its chemistry was harmful for acidosensitive taxa such as Ephemeroptera and Trichoptera. Plecoptera and Chironomidae were the most numerous groups in this stream. The biological recovery of both streams will depend on further chemical improvement in their catchments as well as on the dispersal ability of benthic organisms.     

The influence of stream habitat and water quality on macroinvertebrate communities in degraded streams of northwest Mississippi

Streams in the loess hills of northwest Mississippi have undergone dramatic physical changes since European settlement and both physical and water quality processes may play a role in influencing biotic communities of these stream systems. The objectives of this study were to identify the response of macroinvertebrate taxa to water quality and habitat parameters in streams of northwest Mississippi, examine the efficacy of an a priori classification system of stream channel evolution and condition class using macroinvertebrate communities, and examine short-term (<2 yr) temporal variation of macroinvertebrate communities. Separation of sites based on four condition classifications was not distinct. However, best attainable sites did plot together in an ordination analysis suggesting similarity in macroinvertebrate communities for least disturbed sites. Similarly, for stage of channel evolution, sites characterized by lack of bank failure and sinuous fluvial processes had relatively similar macroinvertebrate communities. Ordination analysis also indicated high temporal variation of macroinvertebrate communities. Reference sites (best attainable and stable sites) had more similar communities between years than unstable and impacted sites. Results of this study: (1) suggest total solids, total phosphorus concentration, percent substrate as sand, ammonia concentration, and conductivity were important variables for structuring stream macroinvertebrate communities in northwest Mississippi, (2) identify potential indicator taxa for assessing such streams based on water quality and physical habitat, (3) provide support for current a priori site classifications at the best attainable (least impacted) category relative to the macroinvertebrate communities, and (4) demonstrate that between-year variation is an important factor when assessing streams of north Mississippi and this variability may be related to the degree of stream degradation.     

Littoral macroinvertebrates of acidified lakes in the Bohemian Forest

Mountain lakes in the Bohemian Forest, on both the Czech and German sides, were atmospherically acidified mainly in the 1960s–1980s and have since been recovering from acidification. In 2007, we performed the first complete study on littoral macroinvertebrates in all eight lakes. The goals of the study were to 1) compare macroinvertebrates in the lakes during the process of recovery and 2) investigate relations between the occurrence of taxa and water chemistry. Lake water pH varied from 4.6 to 5.7, concentrations of dissolved reactive Al and labile Al ranged from 118–601 and 11–470 μg L^?1, respectively, and DOC concentrations were < 6 mg L^?1. Altogether 73 taxa were identified from all lakes; a positive relationship was found between pH and the number of macroinvertebrate taxa. The highest number of taxa was found in the least acidic lakes Laka and Grosser Arbersee, including the mollusk Pisidium casertanum. In contrast, the lowest diversity was found in the most acidified ?ertovo jezero. Cluster analyses of macroinvertebrates and water chemistry suggested pH as the key factor influencing the occurrence of macroinvertebrate taxa. An interesting finding was the occurrence of the boreo-montane water beetle Nebrioporus assimilis in Prá?ilské record of this species in the Czech Republic since 1960.     

Nitrogen retention in headwater streams: the influence of groundwater-surface water exchange

Groundwater-surface water (GW-SW) interaction lengthens hydraulic residence times, increases contact between solutes and biologically active surfaces, and often creates a gradient of redox conditions conducive to an array of biogeochemical processes. As such, the interaction of hydraulic patterns and biogeochemical activity is suspected to be an important determinant of elemental spiraling in streams. Hydrologic interactions may be particularly important in headwater streams, where the extent of the GW-SW mixing environment (i.e., hyporheic zone) is proportionately greater than in larger streams. From our current understanding of stream ecosystem function, we discuss nitrogen (N) spiraling, present a conceptual model of N retention in streams, and use both of these issues to generate specific research questions and testable hypotheses regarding N dynamics in streams.     

Surface‐water availability governs survival of an amphibian in arid mountain streams

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Forest river plants and water quality in Ghana

River plants and water chemistry in wet and dry seasons were sampled in a wide range of rivers with variable catchments in the forest zone of Ghana, in order to examine the relationships between the floristic composition within the river and river water and catchment environmental variables.Plant species occurring in the river or on its seasonally flooded banks along 500 m sample stretches were listed in 26 sites. Sample species richness was low (1–17 species per sample, mean 5.9). Only nine species were recorded that are confined to rivers. Cluster analysis defined five floristic groups which differed in catchment area, geology, turbidity and dissolved minerals.Analysis of water chemistry variables by principal components analysis revealed a strong principal gradient (42% of total variance) related to annual rainfall with low ionic concentrations under high rainfall. The second component described seasonal differences in water chemistry. Nitrate and chloride were more concentrated in the dry season, but sulphate and calcium were more concentrated in the wet season.Catchments with higher forest cover yielded more oligotrophic and less turbid water. Catchment geology influenced water chemistry so that sandstone areas yielded clear water, and ancient peneplain areas with bauxitic soil were characterised by exceptionally low silicon concentrations.The association of macrophyte composition with river chemistry and catchment conditions was somewhat tenuous, due to the low number of species, but the low turbidity, oligotrophic rivers under high rainfall and with a high percentage of species-rich forest cover were the more species rich. Prediction of river water quality at the scale of this study are more readily made from a knowledge of catchment rainfall and forest cover than from assessments of river plant composition.     

Biological recovery of the Bohemian Forest lakes from acidification

A limnological survey of eight small, atmospherically acidified, forested glacial lakes in the Bohemian Forest (?umava, Böhmerwald) was performed in September 2003. Water chemistry of the tributaries and surface layer of each lake was determined, as well as species composition and biomass of the plankton along the water column, and littoral macrozoobenthos to assess the present status of the lakes. The progress in chemical reversal and biological recovery from acid stress was evaluated by comparing the current status of the lakes with results of a survey four years ago (1999) and former acidification data since the early 1990s. Both the current chemical lake status and the pelagic food web structure reflected the acidity of the tributaries and their aluminium (Al) and phosphorus (P) concentrations. One mesotrophic (Ple?né jezero) and three oligotrophic lakes (?erné jezero, ?ertovo jezero, and Rachelsee) are still chronically acidified, while four other oligotrophic lakes (Kleiner Arbersee, Prá?ilské jezero, Grosser Arbersee, and Laka) have recovered their carbonate buffering system. Total plankton biomass was very low and largely dominated by filamentous bacteria in the acidified oligotrophic lakes, while the mesotrophic lake had a higher biomass and was dominated by phytoplankton, which apparently profited from the higher P input. In contrast, both phytoplankton and crustacean zooplankton accounted for the majority of plankton biomass in the recovering lakes. This study has shown further progress in the reversal of lake water chemistry as well as further evidence of biological recovery compared to the 1999 survey. While no changes occurred in species composition of phytoplankton, a new ciliate species was found in one lake. In several lakes, this survey documented a return of zooplankton (e.g., Cladocera: Ceriodaphnia quadrangula and Rotifera: three Keratella species) and macrozoobenthos species (e.g., Ephemeroptera and Plecoptera). The beginning of biological recovery has been delayed for ～20 years after chemical reversal of the lakes.     

Variability of water temperature may influence food-chain length in temperate streams

Nutrient enrichment may alter population dynamics of species in different ways depending on their life strategies. The aim of this study was to test the effect of different nutrient concentrations on the population development of two bacterivorous freshwater nematodes, Bursilla monhystera and Plectus aquatilis. Microcosms with autoclaved natural sand from a pristine stream (Fuirosos, NE of Spain) were enriched with different levels of phosphate, nitrate and ammonia as inorganic nutrients and glucose as a biodegradable dissolved organic carbon source. Although leaching of carbon and nutrients from the detritus fraction in the sediment initially may have overruled differences between treatments, later samplings revealed bottom-up control, with Bursilla monhystera abundances positively correlated to bacterial abundances at high nutrient concentrations. Nevertheless, there were several indications that nematodes in turn affected microbial abundance, most likely through excretion of ammonia and through grazing. In contrast to B. monhystera, Plectus aquatilis at high nutrient concentrations showed a unimodal abundance curve, while not increasing in abundance at low nutrient concentrations. Glucose enrichment did not have any stimulatory effect on either microbial or nematode abundances, probably as a result of unfavourable C:N:P stoichiometry. P enrichment, by contrast, stimulated microbial and Bursilla abundances. Our results indicate that episodic nutrient enrichment may affect populations of bacterial-feeding nematodes in the short term. Their longer-term dynamics may, however, be more dependent on leaching of carbon and nutrients from the pools of sediment-bound detritus.     

The influence of water chemistry on the enzymatic degradation of leaves in streams

1. Aquatic hyphomycetes degrade leaf litter in both softwater and hardwater streams. During growth on leaves, these fungi secrete an array of extracellular polysaccharidases that are differentially affected by pH. Hydrolytic enzymes exhibit acidic pH optima, whereas pectin lyases have neutral to alkaline pH optima. 2. Enzyme activities associated with microbial communities colonizing yellow poplar (Liriodendron tulipifera) leaves submerged in an acidic (pH 6.3), softwater stream were compared with those occurring in an alkaline (pH 8.2), hardwater stream. In addition to pH differences, the hardwater stream had higher nutrient concentrations and higher temperatures than the softwater stream. Conditions in the hardwater stream favoured greater microbial growth, fungal activity, rates of leaf breakdown and softening. However, activities of hydrolytic enzymes (xylanase, endocellulase, galacturonanase) were lower in the hardwater stream than in the softwater stream. Consequently, activities of these hydrolytic enzymes were not good indicators of leaf breakdown in these streams. 3. In contrast, the activities of pectin lyase were higher in the hardwater stream than in the softwater stream, corresponding to the greater rates of leaf breakdown and softening that occurred in the hardwater stream. These results support previous findings that pectin lyase is closely associated with the softening and maceration of leaf detritus and suggest that pectin degradation is a key process in the initial stages of leaf breakdown.     

Communities of oligochaetes in mountain streams of Poland

This study compares the structure of oligochaete communities in mountain streams of Poland. These streams can be divided into three groups. First, those dominated by the Enchytraeidae (Mesenchytraeus armatus), second where the Naididae, Nais bretscheri, Nais alpina, Nais communis or Nais variabilis prevail and third, where the Lumbriculidae, represented by Stylodrilus heringianus, and in one case by Stylodrilus parvus, are dominant. The nature of the stream bottom is the main factor determining the structure of the community, but geographic location is also important.     

Studies on mountain streams in the English Lake District

Sodium and potassium in streamwater were measured over a period of 2 years, and concentrations of other major ions were occasionally monitored. The supply of sodium, potassium and calcium in rainfall was measured over a period of 1 year. A tentative budget is given for annual income and output of sodium, potassium and calcium in the Duddon catchment. Sodium and potassium concentrations in streamwater were independent of stream discharge; both ions displayed an annual cycle of high concentrations in winter and low concentrations in summer. The input of sodium was dependent on rainfall, wind direction and wind speed; 40% of the annual supply in rain was precipitated in the autumn. Sodium income in rainfall during the remaining 9 months of the year was insufficient to balance the output in streamwater. Annual income of potassium in rainfall was equal to annual output in streamwater. But potassium was retained on the catchment during spring and summer and was slowly released to the streams in autumn and winter. Only about 10% of the annual calcium output was derived from atmospheric sources.     

Diatom communities of acidic mountain streams in Poland

A comparison has been made of the species composition of diatom communities developing in acidic Polish mountain streams which flow over calcium-poor substrates: sandstones in the Silesian Beskid (section of the Western Carpathians), the witokrzyskie Mts, and over granite in the Karkonosze range (in the Sudetic Mts). The number of taxa and diversity of the diatom assemblages decreased along a decreasing pH gradient. The correlation between pH and the number of taxa was positive and significant (r ² = 0.69, p < 0.005). A small number of species (< 20) and low diversity were found in the communities developing in strongly acidic streams such as in the witokrzyskie Mts with pH 4.1–5.2, and in the Silesian Beskid with pH 3.5–4.0. In the stream of the Karkonosze Mts, with pH 5.2–6.0, the communities were characterized by their greater number of species and higher diversity.Acidobiontic and acidophilous diatoms were generally dominant. The pH-indiferent forms were less abundant, and their proportion increased above pH 5.0. Eunotia exigua, E. paludosa var. trinacria, E. tenella and Pinnularia subcapitata dominated in streams with the lowest pH, while E. exigua, E. sudetica and Achnanthes kryophila predominated in a stream with water pH above 5.2. Eunotia exigua, a common acidobiontic species was present in all the examined communities, and was a strong dominant in waters of pH 5.0. A corresponding decrease in abundance of E. exigua was observed with an increase in pH.     

Invertebrate communities and hydrological variation in Cairngorm mountain streams

Macroinvertebrates, discharge and 16 chemical variables were monitored over a 14-year period in four small streams (catchment area <15 km²) in the Cairngorm mountains, Scotland. Canonical Correspondence Analysis (CCA) was used to assess relationships between invertebrates and environmental conditions on the day of sampling, average conditions over the preceding 1, 2 and 3-month periods and indices of hydrological and hydrochemical variation over preceding monthly intervals.CCA detected subtle inter-catchment differences in invertebrate community structure, with catchments separated along axes representing streamwater calcium, alkalinity and total organic carbon concentrations. Invertebrate communities varied seasonally, with spring, summer and autumn samples separated along CCA axes representing temperature, orthosilicate and discharge. Hydrochemically, spring was the most variable season, characterised by increased frequency of both high and low flow events and acid, snowmelt episodes. In two of the streams, invertebrate community structure varied more in spring than in other seasons.CCA ordinations using indices of hydrological and hydrochemical variation over preceding time periods were more successful (increased eigenvalues) at explaining temporal variation in invertebrate community structure than those using conditions on the day of sampling or average conditions over preceding time periods. For one of the catchments, 40% of the seasonal and between-year variation over the 14-year period could be explained by the frequency of high and low flow events, maximum and minimum water temperatures and acid episodes in the two months prior to the invertebrate samples being collected. The single most important flow parameter (longest CCA arrow) was the frequency of high flow events greater than three times the median discharge.No significant trends in invertebrate community composition were found in any of the streams over the 14-year period so, despite the apparent importance of hydrological and hydrochemical variation, communities appeared stable over the long-term.     

Phytobenthos of the River Tees and its tributaries

SUMMARY. A standard method is given for describing plant communities in fast-flowing streams and rivers. This involves the selection of a representative 10-m length of stream (termed a reach) which can be re-located exactly. Various estimates of the relative areas covered by different physiognomic forms and the relative proportions of species present are then combined to give a 'semi-quantitative' account, which can be compared with data collected at other sites or times. The method has been applied to six sites on the River Tees system. A site below Cow Green reservoir with markedly regulated flows, differs from the others in various ways. Bryophytes show a greater cover here than elsewhere throughout the year and a conspicuous cover of Phormidium occurs in autumn. Filamentous green algae of many different species are abundant at this site in late summer and early autumn. At the most downstream site where such seasonal growths also occur, a single species, Cladophora glomerata , is dominant. Conspicuous spring diatom 'bursts' occurred at the two upstream sites and a month later at the two downstream sites.     

Substratum associations of benthic invertebrates in lowland and mountain streams

The preferences of aquatic invertebrate species for specific substrata at the river bottom have been subject of many studies. Several authors classified the substratum preferences of species or higher taxonomic units. Most of these compilations, however, are based on literature analyses and expert knowledge as opposed to the analysis of original data. To enhance our knowledge of invertebrate substratum preferences, we applied a ‘Multi-level pattern’ analysis based on almost 1000 substrate-specific invertebrate samples. The samples were taken in 18 streams in Germany, the Netherlands and Austria, comprising a total of 40 sampling sites and equally covering lowland and mountain streams. The main objectives of our analysis were (I) to derive substratum preferences of taxa in lowland and mountain streams, (II) to compare the preferences with existing data and (III) to compare species substratum associations between lowland and mountain streams. Of the 290 taxa analyzed, 188 were associated significantly to specific substrata. Twenty-five taxa in lowland streams and 51 taxa in mountain streams prefer one or two substratum types (of nine substratum types considered in total). In contrast, 112 species (mountain streams n = 84, lowland streams n = 28) are associated significantly with a broader range of substrata. We compared the classifications derived from our data analysis with those provided in the freshwaterecology.info database (www.freshwaterecology.info). Our results support the existing classifications of substratum preferences in most cases (70%). For 25 species, substratum preferences for both lowland and mountain streams were derived, many of them indicating different substratum associations in the two stream groups. As substratum preferences differed between closely related species, preferences should always be given at the species level as opposed to coarser taxonomic units.     

Abundance and characteristics of the recreational water quality indicator bacteria Escherichia coli and enterococci in gull faeces

AIMS: To evaluate the numbers and selected phenotypic and genotypic characteristics of the faecal indicator bacteria Escherichia coli and enterococci in gull faeces at representative Great Lakes swimming beaches in the United States. METHODS AND RESULTS: E. coli and enterococci were enumerated in gull faeces by membrane filtration. E. coli genotypes (rep-PCR genomic profiles) and E. coli (Vitek GNI+) and enterococci (API rapid ID 32 Strep and resistance to streptomycin, gentamicin, vancomycin, tetracycline and ampicillin) phenotypes were determined for isolates obtained from gull faeces both early and late in the swimming season. Identical E. coli genotypes were obtained only from single gull faecal samples but most faecal samples yielded more than one genotype (median of eight genotypes for samples with 10 isolates). E. coli isolates from the same site that clustered at >/=85% similarity were from the same sampling date and shared phenotypic characteristics, and at this similarity level there was population overlap between the two geographically isolated beach sites. Enterococcus API(R) profiles varied with sampling date. Gull enterococci displayed wide variation in antibiotic resistance patterns, and high-level resistance to some antibiotics. CONCLUSIONS: Gull faeces could be a major contributor of E. coli (10(5)-10(9) CFU g(-1)) and enterococci (10(4)-10(8) CFU g(-)1) to Great Lakes recreational waters. E. coli and enterococci in gull faeces are highly variable with respect to their genotypic and phenotypic characteristics and may exhibit temporal or geographic trends in these features. SIGNIFICANCE AND IMPACT OF THE STUDY: The high degree of variation in genotypic or phenotypic characteristics of E. coli or enterococci populations within gull hosts will require extensive sampling for adequate characterization, and will influence methods that use these characteristics to determine faecal contamination sources for recreational waters.     

Effects of dispersed recreational activities on the microbiological quality of forest surface water.

The microbiological quality of forest surface waters in the Greenwater River watershed was examined to investigate the influence of heavy motorized camping in an area with no sanitary facilities. Indicator densities increased during weekend human-use periods when compared to weekdays. Increases in indicator densities were also noted downstream from heavily used camping areas when compared to upstream sites. Seasonal, weekly, and diurnal fluctuations in indicator densities were observed. This study suggests that potential health hazards exist in this watershed during periods of human use.     

Temporal and altitudinal variations in the attached algae of mountain streams in Colorado

Attached algae were examined from eight sites in Central Colorado streams (five sites on St. Vrain Creek and three on the Snake River) between June and November, 1995. The sites ranged in elevation from 1600 m to 3500 m a.s.l.(plains zone to alpine zone). Seasonal variation in algal communities were qualified in forms of species composition and abundance (cell counts and biovolumes). The Ochiai coefficient of similarity was used to estimate degree of similarity between communities at different times, on different streams, and at different locations on the same stream. The composition of communities across streams for alpine and foothills zones was very close, but montane communities differed greatly across streams (similarity < 0.1). Temporal variability of attached algae was almost absent in the alpine zone, but was high in other zones. The composition of the alpine community in August developed downstream with a temporal shift: October in the montane and foothills zones, November in the plains zone. This revised version was published online in July 2006 with corrections to the Cover Date.     

Critical influence of seasonal sampling on the ecological quality assessment of small headwater streams

Variability in the ecological quality assessment of reference sites was tested on small headwater streams in Ireland. Although headwater streams constitute a large portion of the river channel network, they are not routinely monitored for water quality. Various metrics were used including the Irish Q-value and the newly developed Small Streams Risk Score (SSRS), and metrics applied elsewhere in the Atlantic biogeographic region in Europe, including the Biological Monitoring Working Party score (BMWP), the Average Score per Taxon (ASPT), the Ephemeroptera, Plecoptera and Trichoptera taxa (EPT), the Belgium Biotic Index (BBI) and the Danish Stream Fauna Index (DSFI). The AQEM (version 2.5a) assessment software was used to apply some of these metrics. The spring and summer datasets are used to test the performance of biotic metrics with respect to season, and the applicability of their use to assess the ecological quality of wadeable streams. The quality status of most sites assigned by the various metrics was high using the spring invertebrate data, and an apparent considerable deviation in quality status occurred when the summer data was applied. Seasonal differences were noted using all the biotic indices and are attributed to the absence of pollution-sensitive groups in summer. Seasonal variability in the water quality status was particularly evident in acidic streams draining non-calcareous geologies with peaty soils that had relatively lower numbers of taxa. Some indices applied reflect a greater seasonal difference in the quality category assigned. The least amount of variability between seasons was obtained using the ASPT and the SSRS risk assessment system. Results suggest that reference status is reliably reflected in spring when more pollution-sensitive taxa were present, and that a new ecological quality assessment tool is required for application in summer when impacts may be most severe. This highly heterogeneous freshwater habitat seems to have too few taxa present in the summer to reliably determine the ecological quality of the stream using the available indices. Handling editor: R. Bailey